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I have a steel post set in limestone, about 18-20 inches deep, with some concrete around it.

I just noticed that I have about 6 inches of water inside the post. The limestone had a small seam in it and I believe the water seeps through it. I am concerned about long term corrosion.

I am about to cap the post, so I will have no access to it in the future. What can I do to prevent/slow the corrosion?

A. Nothing. Do not worry about it.
B. Fill the post with crushed limestone 12 inches above grade.
C. Fill the post with concrete 12 inches above grade.
D. Install a fitting in the post and dump some concentrated washing soda solution or powder once or twice per year to raise pH.
E. Some type of cathodic protection.
F. Other.

I am leaning toward B. This would be easy to accomplish and inexpensive, and limestone is supposed to raise pH level, which I think should slow corrosion.

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    $\begingroup$ I'm no expert on the chemistry stack exchange, but I think you may get a more practical answer on Home Improvement $\endgroup$ – Shokhet Mar 26 '17 at 2:51
  • $\begingroup$ Perhaps. I am afraid most people do not give this much thought, so the scientific approach might yield better results. $\endgroup$ – mcu Mar 26 '17 at 3:00
  • $\begingroup$ Do you know what kind of steel it is (carbon steel, stainless steel, galvanized)? $\endgroup$ – J. Ari Mar 26 '17 at 16:28
  • $\begingroup$ Just regular carbon steel. $\endgroup$ – mcu Mar 26 '17 at 17:26
  • $\begingroup$ Carbon steel can handle slightly basic conditions, so concentrated soda wouldn't be a go to solution. If the post isn't critical for safely supporting something or a related critical function, I think you can go with the limestone idea. If you could borrow/rent a pump and get rid of the water, that would be ideal. If you poured some concrete, could you use the ready to mix stuff that would react with the water in the post? $\endgroup$ – J. Ari Mar 26 '17 at 18:12

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